Carbon fibers are finding many uses in modern products as reinforcement because of their strength and stiffness. The most common approach to using carbon fibers is as woven fabrics or simply as filaments that are layered down and incorporated into a resin to form a shaped part like a boat hull, a panel for a transportation vehicle, a bicycle frame, or a blade for a wind mill. For such processes, several bobbins of carbon fiber filaments are often mounted on a creel, and the filaments are pulled together as needed. For example, a creel of bobbins may feed a beaming process, a weaving process, or even a process of forming a shape by winding filaments. However, it is fairly common to have partial bobbins left over during both the fiber manufacturing and weaving processes that are considered waste.
Attempts have been made to use the carbon fibers remaining on those partial bobbins by cutting them into staple fibers and incorporating them with other fibers into nonwovens that are subsequently used as reinforcement materials in composite structures. One approach to make such nonwovens that can be used in molding applications consists of first forming a nonwoven by carding a blend comprising thermoplastic fibers (i.e. matrix fibers) and reinforcement fibers where the matrix thermoplastic fibers have a melting point substantially lower than the melting or degradation temperature for the reinforcement fibers. Next, the nonwoven web is needled to both consolidate it and achieve a higher density. This nonwoven subsequently is used to mold a part by using heat and pressure. During this process, the majority of the matrix fibers are melted and the resulting polymer flow encases the reinforcement fibers. However, such existing nonwovens have been unable to achieve sufficient strength while simultaneously exhibiting a low void volume.
Therefore there at least remains a need for a carbon nonwoven that can be consolidated by molding the nonwoven into a thin part in such a way as achieve both a high strength and a low void volume.